> Would something like passing a mem=xx cmdline on x86_64 be sufficient to test this?

I think so, though I admit I don't remember using this personally sincethe introduction of e820 RAM mapping support.Dmesg will show if the memory is limited. For the swiotlb to effectivelydisable no RAM > 0x100000000 may be used.

But this test isn't IMHO terribly important at this point - the drivermakes invalid use of the DMA API and it has to change. The test couldonly explain _how_ exactly does it fail, we already know _why_ it does.-- Krzysztof Halasa